package com.baomidou.kisso.common.bcprov.asn1;

import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;

import com.baomidou.kisso.common.bcprov.util.io.Streams;

class DefiniteLengthInputStream extends LimitedInputStream {

	private static final byte[] EMPTY_BYTES = new byte[0];

	private final int _originalLength;

	private int _remaining;


	DefiniteLengthInputStream( InputStream in, int length ) {
		super(in, length);

		if ( length < 0 ) {
			throw new IllegalArgumentException("negative lengths not allowed");
		}

		this._originalLength = length;
		this._remaining = length;

		if ( length == 0 ) {
			setParentEofDetect(true);
		}
	}


	int getRemaining() {
		return _remaining;
	}


	public int read() throws IOException {
		if ( _remaining == 0 ) {
			return -1;
		}

		int b = _in.read();

		if ( b < 0 ) {
			throw new EOFException("DEF length " + _originalLength + " object truncated by " + _remaining);
		}

		if ( --_remaining == 0 ) {
			setParentEofDetect(true);
		}

		return b;
	}


	public int read( byte[] buf, int off, int len ) throws IOException {
		if ( _remaining == 0 ) {
			return -1;
		}

		int toRead = Math.min(len, _remaining);
		int numRead = _in.read(buf, off, toRead);

		if ( numRead < 0 ) {
			throw new EOFException("DEF length " + _originalLength + " object truncated by " + _remaining);
		}

		if ( (_remaining -= numRead) == 0 ) {
			setParentEofDetect(true);
		}

		return numRead;
	}


	byte[] toByteArray() throws IOException {
		if ( _remaining == 0 ) {
			return EMPTY_BYTES;
		}

		byte[] bytes = new byte[_remaining];
		if ( (_remaining -= Streams.readFully(_in, bytes)) != 0 ) {
			throw new EOFException("DEF length " + _originalLength + " object truncated by " + _remaining);
		}
		setParentEofDetect(true);
		return bytes;
	}
}
